This invention relates in general to vehicle brake assemblies and in particular to an improved structure for a brake rotor/drum for use in such a vehicle brake assembly and method for producing the same.
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system includes either a disc brake assembly or a drum brake assembly for each of the wheels. The brake assemblies are typically actuated by hydraulic or pneumatic pressure generated by an operator of the vehicle depressing a foot pedal, pulling a hand lever, and the like. The structure and operation of the brake assemblies, as well as the actuators therefor, are well known in the art.
A typical disc brake assembly includes a rotor which is secured to the wheel of the vehicle for rotation therewith. The rotor includes a pair of opposed friction plates which are selectively engaged by portions of a caliper assembly. The disc brake assembly includes a caliper assembly of either a "floating" type or a "fixed" type. A floating caliper type of disc brake assembly is usually used on automobiles and light and medium duty trucks. A conventional floating caliper type of disc brake assembly includes a brake caliper which is supported by a pair of pins or on a pair of guide rails for sliding movement relative to an anchor plate which is secured to a fixed, non-rotatable component of the vehicle. A fixed caliper type of disc brake assembly is sometimes used in automobiles and light and medium duty trucks. A conventional fixed caliper type of disc brake assembly (shown generally at 114 in prior art FIG. 12), includes a brake caliper which is solidly fixed to a fixed, non-rotatable component of the vehicle. In both types of disc brake assemblies, a pair of brake shoes are supported by the disc brake assembly on opposite sides of the rotor for sliding movement relative thereto. The brake shoes are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from the opposed friction plates of the rotor, and a braking position, wherein they are moved into frictional engagement with the opposed friction plates of the rotor. When the operator of the vehicle depresses the brake pedal, the piston urges the brake shoes from the non-braking position to the braking position so as to frictionally engage the friction plates of the rotor and thereby slow or stop the rotation of the associated wheel of the vehicle.
A typical drum brake assembly includes a backing plate which is secured to a fixed, non-rotatable component of the vehicle, such as the vehicle axle housing. A pair of opposed arcuate brake shoes are supported on the backing plate for selective movement relative thereto. Each of the brake shoes has a friction pad secured thereto. The brake drum assembly further includes a hollow cylindrical brake drum which is secured to a vehicle wheel for rotation therewith. The hollow interior of the brake drum defines an inner cylindrical braking surface. The brake drum is disposed adjacent to the backing plate such that the brake shoes extend within the cylindrical braking surface. When the operator of the vehicle depresses the brake pedal, the brake shoes are moved outwardly apart from one another such that the friction pads frictionally engage the cylindrical braking surface of the brake drum. Such frictional engagement causes slowing or stopping of the rotational movement of the brake drum and, therefore, the wheel of the vehicle in a controlled manner.
When the above brake rotor/drum is used in a brake system having an anti-lock brake feature, the brake rotor/drum can be provided with integrally cast teeth. As shown in prior art FIG. 12, the teeth 110 provided in a brake rotor 112 of a disc brake assembly 114 (or a brake drum (not shown) of a drum brake assembly (not shown)) are "read" by an anti-lock brake sensor 116 in order to generate a signal to the anti-lock brake system. Typically, the teeth are cast in the brake rotor/drum during the casting process, and then subsequently machined to predetermined tolerances. The casting process typically used to cast the brake rotor/drum is a green sand casting process. While the use of such a casting process appears to result in generally uniform teeth, the shape of the teeth can vary due to the nature of the sand casting process. As a result, the "set up" area provided for the teeth by the sand casting process can make it difficult to machine the teeth to tight tolerances that are necessary for proper operation of the anti-lock brake system. Thus, it would be desirable to provide an improved structure for a brake rotor/drum having integrally cast teeth and method for producing such a brake rotor/drum which is relatively simple and economical.